I'm helping a friend set up a 2.1 system for a house he is building and I could use some assistance determining which drivers to use. The speakers will go with a sub (probably a Stereo Integrity 18") mounted in the middle of the two speakers which are on either side of a TV.

The speakers are going to be in-walls with us building an actual box that will slide into the wall. Only the front baffle will extend out past the sheet rock. Due to this limited depth the box isn't going to have much airspace.

Right now I think I can get at most about .3 cubic feet although something in the .2 to .25 would be better as WAF is definitely priority number one on the project (I'm doing all I can to keep sound quality on equal footing).

I'm currently looking at doing a TMM setup using the XT25 in a waveguide (inspired by SpinMonster's design). What mid drivers would work with little airspace but still get down low enough to cross over to the sub? 6.5" is the maximum diameter that will fit. With the waveguide I plan on crossing over the high end around 2k. I'm thinking with the limited airspace it will be a sealed box. Also with these being in-walls can I expect much of a boost to the low end from the lower frequencies sound radiating off of the wall?

It is a large space (30' x 26') and the system will be used for movies and music (50/50).

I'm helping a friend set up a 2.1 system for a house he is building and I could use some assistance determining which drivers to use. The speakers will go with a sub (probably a Stereo Integrity 18") mounted in the middle of the two speakers which are on either side of a TV.

The speakers are going to be in-walls with us building an actual box that will slide into the wall. Only the front baffle will extend out past the sheet rock. Due to this limited depth the box isn't going to have much airspace.

Right now I think I can get at most about .3 cubic feet although something in the .2 to .25 would be better as WAF is definitely priority number one on the project (I'm doing all I can to keep sound quality on equal footing).

I'm currently looking at doing a TMM setup using the XT25 in a waveguide (inspired by SpinMonster's design). What mid drivers would work with little airspace but still get down low enough to cross over to the sub? 6.5" is the maximum diameter that will fit. With the waveguide I plan on crossing over the high end around 2k. I'm thinking with the limited airspace it will be a sealed box. Also with these being in-walls can I expect much of a boost to the low end from the lower frequencies sound radiating off of the wall?

It is a large space (30' x 26') and the system will be used for movies and music (50/50).

Thanks for the help and let me know if more information would help.

Cheers!

... at a minimum. With this large space, why bother going into the walls. If you must, then build the front wall hollow with two runs of 2 x 4 studding to get decent sized wall pockets for the enclosures. Some of the remaining void space can be used for built-in display shelves and storage cabinets. Do not build loudspeaker units into the walls, adjustable toe-in will be needed for right and left units. To do justice to this large listening space, avoid using wimpy loudspeaker units

I had the same dilemma when looking for a suitable woofer to play in the tiny 2l sealed encosure of the BMW 5-series. Out of about 15 drivers tested, all 5.25", the SB15MFC 4 ohm version was superior in low end extension. It also has a very nice mid and with little work to address the peak in freq. response, could be crossed easily at 3-3.2Khz.
The XT25 is a very nice tweeter but people usually get lured by its low Fs and low price. You`ll need an RLC circuit with it however, otherwise it rings badly under 2Khz - very audible. To absolutely level down the impedance peak, use a parallel notch centered at 550Hz of 1mH/82uF/3.9ohm. Depending on your friend`s listening spl, you could do 12db at 2.2-2.3Khz but if he plays it with more than 20 watts, it will distort a lot. Better used 2.5Khz up if a shallower slope is preferred or in a waveguide.

Mario - The plan is to use a waveguide with the XT25 but I'm open to other tweeter recommendations with and without a waveguide.

whgeiger - I'm bothering going into walls because the other option I was given was for the speakers to be in a credenza that is on the floor. The main listening location will be less than 15 degrees off axis so no toe-in won't be too much of an issue. The wall is already framed in so increasing the depth of it isn't an option (I will ask and double check though).

Inductor - The entire box volume will be around .25 cubic feet +/- .05 cubic feet (7 liters +/- 1.5 liters). This space will house two midwoofers. 6.5" is just the largest diameter that will fit. Any two drivers 5" to 6.5" would be fine. I'd like to use two midwoofers for the extra efficiency.

Another option would be to just use the wall cavity as the enclosure as a infinite baffle setup. There would be 2.5 cubic feet of space in one cavity and 4 cubic feet in the other. Anything special I should look at in midwoofers for this sort of setup?

For want of a better option : Zaph|Audio - ZDT3.5
Build it into the wall but use the centre channel crossover *.

Built as a TMBB or BTMB tweeter 12" below seated ear height.
Built as a MTBB or BMTB tweeter 12" above seated ear height.

Now a clever bit : Insert stiff foam (sort of stuff used for seating)
into the wall cavity to define about 1 cuft of rear space. 1' to 2'.
Though porous air flow is poor and it will define a lossy air space.
Normal box stuff in the air space, foam on the back, and stuff.
The seating foam will kill any issues of the vertical airspace.

rgds, sreten.

* As far as I can work it out the centre channel midrange rise will
be compensated by the wall mounting to end up with something
very near the balance that is intended for normal L&R boxes.

sreten - My thinking for going with TMM is for the increased efficiency and lower distortion on the midbass driver. 6.5" is just the maximum width I can use. That isn't necessarily the size I'm looking at. Smaller is fine.

With the crossover to the sub being in the 80 to 100 Hz region so the mains don't need to go very deep.

I like the idea of using the wall cavity itself as the box. My concern with that it will basically end up being a box that is partly made out of sheet rock. With the sub taking care of the low end is this not a concern?

Also, do you really think there will be much of a benefit going with Zaph's 3.5 way design over using a waveguide with the XT25? SpinMonster got some very good measurements with the waveguide - XT25 combo.

Thanks for the link to Zaph's ZA5 page I hadn't seen that before. His ZA5.3iw is basically what I'm looking to do. I see he gives advice on how to properly setup a wall cavity to use it as the box. I'll be reviewing that in the next couple of days to use some of his ideas.

These are really good (the one'son top). Ans had no issues playing reasonably loud outside. 10 litres (0.35 ft^3) for the 2 silver flute W14. These boxes are 13 litre with the TL for the mid-tweeter, with a dome you can get down to 10 litre (but suffer a loss in fidelity). A more complex (but likely less expensive) XO would be needed.